Global Journal of Researches in Engineering
Electrical and Electronics Engineering
Volume 13 Issue 12 Version 1.0 Year 2013
Type: Double Blind Peer Reviewed International Research Journal
Publisher: Global Journals Inc. (USA)
Online ISSN: 2249-4596 & Print ISSN: 0975-5861
High Speed Voltage Switching Converter from Single Phase to
Three Phase: A Design and Implementation Process
By Abdul Rehman & Muhammad Shakeel Faridi
University of South Asia Lahore, Pakistan
Abstract - A single phase to three phase converter topology for domestic use and for small
industries is presented in this project. Phase converter, included in this project, is a device that
supplies three phase power from a single phase source to power inductive, resistive and
capacitive loads with distinct advantages over any existing converter device. Three phase
converters are finding increased applications in industrial environment with greater demand for
high voltage, high power processing techniques with improved efficiency. The essential
advantage is the improvement in the improvement in the output voltage signal quality using
devices of low voltage rating with lesser switching frequency, thereby increasing the overall
efficiency of the system. This converter is applied to drive the motor.
GJRE-F Classification : FOR Code: 290901
HighSpeedVoltageSwitchingConverterfromSinglePhasetoThreePhaseADesignandImplementationProcess
Strictly as per the compliance and regulations of :
© 2013. Abdul Rehman & Muhammad Shakeel Faridi. This is a research/review paper, distributed under the terms of the Creative
Commons Attribution-Noncommercial 3.0 Unported License http://creativecommons.org/licenses/by-nc/3.0/), permitting all non
commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
High Speed Voltage Switching Converter from
Single Phase to Three Phase: A Design and
Implementation Process
Abdul Rehman α & Muhammad Shakeel Faridi σ
T
I.
In single phase AC electric power system, the
power falls to zero three times during one complete
cycle i.e. at the interval of 0, π (180 o) and 2π (360 o) as
shown in fig. 1 below. Whereas in three phase electric
system the power never falls to zero and a continuous
same power is delivered to the load at all time as shown 33
in fig. 2 below.
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domestic use and for small industries is presented in this
project. Phase converter, included in this project, is a device
that supplies three phase power from a single phase source to
power inductive, resistive and capacitive loads with distinct
advantages over any existing converter device. Three phase
converters are finding increased applications in industrial
environment with greater demand for high voltage, high power
processing techniques with improved efficiency. The essential
advantage is the improvement in the improvement in the
output voltage signal quality using devices of low voltage
rating with lesser switching frequency, thereby increasing the
overall efficiency of the system. This converter is applied to
drive the motor.
Introduction
his type of converter is required in those areas
where the three phase electric power is not
present. Most of these areas include domestic
areas because most of the domestic use appliances are
powered by single phase electric power. One of the
reasons of not giving three phase electric power to the
domestic customers is its high cost of connection
installation. But still, if any customer wants to run a three
phase appliance on a single phase electric power, the
single phase to three phase converter can be used. The
reason of using three phase power is that three phase
appliances are available in high ratings as compared to
appliances available in single phase. For example
[1,2,3]
1) In case of loads, three phase motors are more
compact and less costly than a single phase motor
of same voltage and rating. Moreover single phase
AC motors above 10 HP (7.5 kW) are rarely
available. Three phase motors have self-starting
torque because they can produce rotating magnetic
field whereas single phase motors requires a
special starting winding.
2) From generation point of view, the three phase AC
generators are smaller in size as compared to single
phase generators. The kVA rating of three phase
generator is 1.5 times greater than that of single
phase AC generators.
Author α : Department of Electrical Engineering, University of South
Asia Lahore, Pakistan. E-mail : engr.armughal@gmail.com
Author σ : Department of Computer Science, University of Agriculture,
Faisalabad, Pakistan. E-mail : shakeelfaridi@gmail.com
Fig. 1 : One complete cycle of single phase voltage
Fig. 2 : One complete cycle of three phase voltage
Most motors and equipment’s need this
continuous power to run properly.
The above discussion emphasis on a strong
need of efficient and cost effective static single phase to
three phase voltage converter. Previous work done in
this regard has created a wide variety of possible
circuits that could be used for single phase to three
phase voltage conversion but these works have some
disadvantages as well for example in [4] thyristors are
used in combination with L-C components. The
disadvantage of this conversion technique is that the
L-C values must be matched with the load impedances.
Furthermore in [5] the technique proposed has a
disadvantage that only two semiconductor devices are
used for the conversion purpose therefore the
conversion would not be that much accurate i.e. phase
difference between each phase cannot be exactly 120o.
© 2013 Global Journals Inc. (US)
Global Journal of Researches in Engineering ( F ) Volume XIII Issue XII Version I
Abstract - A single phase to three phase converter topology for
High Speed Voltage Switching Converter from Single Phase to Three Phase: A Design and Implementation
Process
In response to above two mentioned techniques
the technique mentioned in this paper will nullify the
above mentioned disadvantages.
Year 2 013
II.
Global Journal of Researches in Engineering ( F ) Volume XIII Issue XII Version I
34
2
Proposed Three Phase Converter
The converter proposed in this project converts
the single phase electric power to three phase electric
power in two steps:
1) POWER CIRCUIT: Conversion of single phase A.C
voltage to D.C voltage i.e. from 220V, 50Hz single
phase A.C supply to 400V D.C supply.
2) CONTROL CIRCUIT: Conversion of D.C voltage to
three phase A.C voltage i.e. from D.C 400V to 380V,
50Hz three phase A.C supply by using PIC
microcontroller.
Both of these steps are described in detail below
a) Power Circuit
The power circuit is that part of the converter in
which rectification is done i.e. single phase A.C voltage
220V, 50Hz is converted to D.C voltage 400V. The
reason of converting 220V A.C to 400V D.C is to get the
three phase voltage of amplitude of 400V which is then
switched with the help of hex-bridge and microcontroller
in such a way to get a three phase voltage with phase
difference of 120o. This rectification can be done by
using a full bride rectifier which can be made either by
using diodes or by using an I.C whose output voltages
are equal to 400V. The full bridge rectifier circuit is
shown in fig. 3.
These 400V D.C produced will be given to the
hex-bridge. The hex-bridge is the heart of three phase
inverter. It takes a D.C voltage and uses six switches
arranged in three legs for switching purpose. The hexbridge used is shown in fig. 4
Fig. 4 : Hex-bridge
In fig. 4 Q1-Q6 are six switching devices and A,
B, C are the three phase output terminals that will be
connected to the motor terminals. There are two types of
switching devices that could be used IGBT or MOSFET.
In this project IGBTs are used instead of MOSFETs
[6,7]. This selection is made on the conditions for which
these two devices are to be used. Mostly the decision is
made keeping two factors in mind
1) Switching frequency
2) Voltage bearing capability of device
The IGBT is chosen for voltages above 1000V,
while the MOSFET is certainly chosen for voltages below
250V. Between 250 to 1000V, some technical papers
prefer MOSFETs and some IGBTs this is shown
graphically in fig. 5
Fig. 3 : Rectifier
The smoothing capacitor is used to remove the
ripples so that we can get a smooth D.C voltage. The
value of this capacitor can be found out by Eq. 1
𝐶𝐶 =
2 (𝑃𝑃𝑜𝑜 )(𝑇𝑇ℎ )
(𝑉𝑉12 − 𝑉𝑉22 ) (𝜂𝜂)
(1)
Where
C = Capacity of filtering capacitor
Po = Output power of the rectifier
Th = Hold-up time
V1 = Input D.C voltage i.e.
Input A.C voltage (rms) x √2
V2 = Input D.C voltage which can hold output voltage
η = Efficiency
© 2013 Global Journals Inc. (US)
Fig. 5 : Regions where IGBTs and MOSFETs are
preferred
As working voltage for the hex-bridge is 400V
D.C and switching frequency is between 20-25 kHz, so
IGBTs are used.
b) Control Circuit
The control circuit is that part of the converter in
which electrical components are used to control the
switching of the six IGBTs to generate three phase 380V,
50Hz voltage with exact phase shift of 120o. To see the
control circuit at a glance, block diagram of control
circuit is shown in fig. 6
As mentioned earlier that a microcontroller is
used to control the switching of the six IGBTs connected
in hex-bridge. Any one output port of the PIC
microcontroller can be used for output signals. Total six
microcontroller pins will be used for output purpose.
These pins will then give signal to each gate terminals of
six IGBTs connected in hex-bridge while travelling
through bridge driving IC. The method used to generate
control signals through microcontroller is pulse width
modulation (PWM) as shown in fig. 7.
35
Fig. 9 : Generation of three phase waveform from the
sine table
Fig. 7 : PWM connected with hex-bridge
The reason of using PWM technique is that a
switching wave of constant magnitude and frequency is
required. The PWM signals are generated in such a way
that three IGBTs will conduct at a time i.e. either one
upper or two lower or two upper and one lower. Upper
and lower IGBTs of the same limb are not made
conductive at the same time otherwise the D.C bus
supply would become short circuited. There is a time
delay given between switching the upper IGBT ON and
lower IGBT OFF and vice versa. This time delay is called
dead time. To control the switching of the upper three
IGBTs three PWMs are required. For switching the lower
three IGBTs the inverted PWM signals of the
corresponding upper IGBTs are used. The three PWMs
used for the three phase sine wave generation are
shown in fig. 8
Fig. 8 : Generation of three phase sine wave using PWM
To control the values of the sine table + offset,
three timers are used. These timers are Timer0, Timer1
and Timer2. The functions performed by each of these
timers is given in table 1
Table 1 : Timers and their functions
Timers
Timer0
Timer1
Timer2
Function
Interrupt timer after
which
duty
cycle
changes
Interrupt timer for the
positive peak of A.C
wave
Interrupt timer for the
negative peak of A.C
wave
Another purpose of using these timer registers
is that as the program for the microcontroller is written in
software and then burned in hardware i.e. in
microcontroller, so the hardware and software PWMs will
be leading or lagging from one another. To control this
problem and to get same PWM signals. The detailed
working of the three timers from this point of view is
discussed below.
1. Timer2
It is an 8-bit timer used to control the timing of
hardware PWMs. The main processor is interrupted
when the Timer2 value matches the PR2 value.
© 2013 Global Journals Inc. (US)
Global Journal of Researches in Engineering ( F ) Volume XIII Issue XII Version I
Fig. 6 : Block diagram of control circuit
In the used PWM technique the duty cycle of
the square wave will determine the phase voltages. To
control this duty cycle a sine table is created in the
program memory which is then transferred to the data
memory upon initialization. A phase shift of 120o is
maintained between phases by using three offset
pointers to the sine table. So a voltage of each phase
will be calculated as
For phase 1: Sine table value + offset1
For phase 2: Sine table value + offset2
For phase 3: Sine table value + offset3
Above explained generation of three phases
with phase shift of 120o is shown graphically in fig. 9
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High Speed Voltage Switching Converter from Single Phase to Three Phase: A Design and Implementation
Process
High Speed Voltage Switching Converter from Single Phase to Three Phase: A Design and Implementation
Process
Year 2 013
2. Timer1
Timer1 is used for setting the duty cycle of the
software PWM. In Timer2 to PR2 match interrupt, the
port pin designated for PWM3 is set to high. Also Timer1
is loaded with the value which corresponds to PWM3
duty cycle. In Timer1 overflow interrupt, the port pin for
PWM3 is cleaned and as a result the hardware and
software PWMs will have the same frequency.
Global Journal of Researches in Engineering ( F ) Volume XIII Issue XII Version I
36
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3. Timer0
After every Timer0 overflow interrupt, the value
pointed by the offset register on the sine table is read.
The value is loaded to the PWM duty cycle registers and
the offset registers are updated for next access.
After the three PWM signals are generated they
are connected to the driver chip that will generate dead
time of 200 ns between upper and lower switches of all
phases.
III.
Simulation & Experimental Results
If we simulate the above discussed method for
the generation of three phase voltage waveform from
single phase voltage then the waveforms obtained from
MATLAB software when the scope is connected across
the PWM generating pins of microcontroller are as
shown in fig. 10
Fig. 10 : Waveforms of all three PWM
The waveforms shown in fig. 10 are switching
waveforms that’s why they are in the form of pulse these
pulses can be created to the A.C waveforms
IV.
Conclusions
The single phase to three phase voltage
converter presented in this research by which three
phase motor is driven is made up of six IGBTs and PWM
technique is used for its switching purpose. The
advantages of using this converter are as follows:
1) The IGBT has the output switching and conduction
characteristic of BJT but is voltage controlled like
© 2013 Global Journals Inc. (US)
MOSFET. In general it means that it has the
advantage of high current handling capability with
the ease of control of MOSFET.
2) The PWM technique used for the switching of IGBTs
has the advantage that power loss in the switching
device is very low because when the switch is OFF
there is practically no current and when the switch in
ON there is almost no voltage drop across the
switch.
References Références Referencias
1. Jeff Keljik, Electricity 3: Power Generation &
Delivery, 9th edition.
2. Irving L. Kosow, Electric Machinery & Transformers,
2nd edition.
3. Scott Landis, The Work Shop Book.
4. S. B. Dewan, M. Showleh, “Steady State Analysis of
Static Single-Phase to Three-Phase Converters”,
IEEE IAS Conf. 1981, pp. 910-915
5. Prasad N. Enjeti, Ashek Rahman, and Ranjit Jakkli,
“Economic Single-Phase to Three-Phase Converter
Topologies for Fixed and Variable Frequency
Output”, IEEE Transactions on Power Electronics,
Vol. 8, No. 3, July 1993.
6. Thomas L. Floyd, Electronic Devices (conventional
current version), 7th edition.
7. http://www.irf.com/technicalinfo/whitepaper/choosewisely.pdf